Ethylene acrylate rubber composition and molded article thereof

ABSTRACT

The present disclosure provides an ethylene acrylate rubber composition which has all of oil resistance, heat resistance and hydrolysis resistance with good balance after molding and cross-linking, and a molded article formed of a cross-linked substance of the ethylene acrylate rubber composition. The ethylene acrylate rubber composition contains 100 parts by mass of an ethylene acrylate rubber, 10 to 50 parts by mass of a plasticizer with an SP value of 7 or more and 0.05 to 30 parts by mass of a cross-linking agent selected from polyvalent aliphatic primary amine or derivatives thereof. The content of a plasticizer with an SP value of less than 7 in the ethylene acrylate rubber is less than 0.1 parts by mass. Further, a molded article formed of a cross-linked product of the ethylene acrylate rubber composition is provided.

TECHNICAL FIELD

The present disclosure relates to an ethylene acrylate rubbercomposition and an ethylene acrylate rubber molded article.

BACKGROUND ART

Acrylic rubber has excellent oil resistance and heat resistance andtheir prices are lower than those of fluoro rubber. Such characteristicsallow acrylic rubber to be widely used as sealing products such as anoil seal, a gasket and an o-ring. However, acrylic rubber is easilyhydrolyzed by water (acid, base) and the water resistance of acrylicrubber is inferior to those of other rubbers such as nitrile rubber andfluoro rubber.

Various types of machine oil such as engine oil are in an automobileengine in which a sealing member made of an acrylic rubber is oftenused. Such machine oil possibly contains a small amount of water such asrain and condensation caused by temperature differences between anengine actuation and stop. Moreover, water caused by burning fuel ispossibly mixed into engine oil in an engine.

Therefore, sealing members made of an acrylic rubber are deterioratedthrough hydrolysis as a result of being exposed to water while they areused. In consequence, a situation in which sealing function is not keptwill occur.

Thereat, in order to improve hydrolysis resistance of acrylic rubber,ethylene acrylate rubbers have been used as rubbers with similarchemical structures to acrylic rubbers and high hydrolysis resistancecompared to acrylic rubber. However, the oil resistance of ethyleneacrylate rubbers is a little inferior to that of acrylic rubbers.

A variety of attempts to improve characteristics of ethylene acrylaterubber compositions by adding third components to ethylene acrylaterubbers are known. For example, Patent Document 1 intends a rubbercomposition to have both heat resistance and cold resistance by addingan ester compound with a specific chemical structure.

PRIOR ART DOCUMENT Patent Document

Patent Document 1: Japanese Patent Application Publication No. H9-12821

SUMMARY Technical Problems

However, in the case of an ethylene acrylate rubber composition, priorarts which attempt to provide an ethylene acrylate rubber compositionhaving all of oil resistance, heat resistance and hydrolysis resistanceafter molding and cross-linking are barely known.

The present disclosure has been made in view of such circumstances.Therefore, the present disclosure provides an ethylene acrylate rubbercomposition which has all of oil resistance, heat resistance andhydrolysis resistance with a good balance between them, and a moldedarticle formed of a cross-linked substance of the ethylene acrylaterubber composition.

Solution to Problem

Inventors of the present disclosure have found out that adding a properamount of an appropriate plasticizer and a suitable cross-linking agentto an ethylene acrylate rubber allows for an ethylene acrylate rubbercomposition which achieves both oil resistance and hydrolysis resistancewith the heat resistance, kept after molding and cross-linking.Accordingly, the present inventors have achieved the present disclosure.The present disclosure has the following composition.

An ethylene acrylate rubber composition of the present disclosure has100 parts by mass of an ethylene acrylate rubber, 10 to 50 parts by massof a plasticizer with an SP value of 7 or more and 0.05 to 30 parts bymass of a cross-linking agent which is selected from polyvalentaliphatic amine or derivatives thereof and a content of a plasticizerwith an SP value of below 7 is less than 0.1 parts by mass.

Besides, the ethylene acrylate rubber composition of the presentdisclosure preferably contains at least either one of 20 to 150 parts bymass of carbon black or 20 to 150 parts by mass of silica.

Moreover, the plasticizer with an SP value of 7 or more in the ethyleneacrylate rubber composition of the present disclosure, is at least oneplasticizer selected from the group consisting of a polyether ester baseplasticizer, a trimellitate ester base plasticizer, a pyromellitateester base plasticizer and a hydrogenated hydrocarbon base plasticizer,preferably.

A molded article of the present disclosure is formed of a cross-linkedsubstance of the ethylene acrylate rubber composition described above.Further, the molded article of the present disclosure is a sealingmaterial preferably.

Advantageous Effects of Disclosure

An ethylene acrylate rubber composition of the present disclosure hasall of oil resistance, heat resistance and hydrolysis resistance aftermolding and cross-linking with good balance. Besides, a molded articleof the present disclosure also has all of oil resistance, heatresistance and hydrolysis resistance in good balance.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be described indetail. However, the scope of the present disclosure is not limited tothe embodiments described below.

An ethylene acrylate rubber composition of the present disclosure has anethylene acrylate rubber, a plasticizer with an SP value of 7 or moreand a cross-linking agent which is selected from polyvalent aliphaticamine or derivatives thereof. Hereinafter, each component forming theethylene acrylate rubber composition of the present disclosure will bedescribed.

(Ethylene Acrylate Rubber)

The ethylene acrylate rubber may be called ethylene acryl rubber or AEM.The ethylene acrylate rubber is a polymer, preferably a terpolymer,which is copolymerized with a cross-linking monomer having across-linking group and main monomer components of the polymer areethylene and acryl acid alkyl ester.

The acrylic acid alkyl ester is, for example, an acrylic acid alkylester with alkyl group having 1 to 20 carbons. Specifically, suchacrylic acid alkyl ester may be methyl acrylate, ethyl acrylate, n-butylacrylate, iso-butyl acrylate, tert-butyl acrylate, propyl acrylate,n-octyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, stearylacrylate or the like. Among such acrylic acid alkyl esters, methylacrylate, ethyl acrylate and n-butyl acrylate are preferable and methylacrylate is more preferable.

The ethylene acrylate rubber employs an ethylene acrylate rubber with across-linking group which is cross-linked to polyvalent aliphatic amineor derivatives thereof. Therefore, the cross-linking group of thecross-linkable monomer composing the ethylene acrylate rubber needs tobe cross-linked to polyvalent aliphatic amine or derivatives thereof.Such a cross-linking group is a carboxyl group, epoxy group, or halogengroup. Among such groups, carboxyl group is preferable to serve as across-linking group.

A cross-linkable monomer with a carboxyl group is given monoalkyl esterof an unsaturated dicarboxylic acid, and unsaturated monocarboxylicacid. The monoalkyl may be methyl, ethyl, propyl, isopropyl, n-butyl,isobutyl or the like and the unsaturated dicarboxylic acid may be maleicacid, fumaric acid, itaconic acid, citraconic acid or the like. Theunsaturated monocarboxylic acid may be acrylic acid, methacrylic acid orthe like. The cross-linkable monomer with a cross-linking group is usedwith about 0.5 to 10 mass percent of a co-polymerization rate in theethylene acrylate rubber.

The ethylene acrylate rubber as mentioned above includes a commerciallyavailable product, such as Vamac (Registered Trademark) G, Vamac(Registered Trademark) GLS (DuPont Dow Elastomers LLC.) or the like.Such ethylene acrylate rubbers may be used alone or in a mixture ofmultiple types of rubbers.

(Plasticizer)

The present inventors assumed that selecting an appropriate plasticizeris important for an ethylene acrylate rubber composition which achievesall of oil resistance, heat resistance, hydrolysis resistance andworkability with good balance, after molding and cross-linking. Namely,the inventor thought it was important that the ideal plasticizer hashigh compatibility with an ethylene acrylate rubber and exists stably ina composition, meanwhile, it is moderately incompatible with oil andwater and compensates oil resistance of an ethylene acrylate rubber.

An SP value is a parameter to evaluate compatibility between twocomponents. The SP value is a Solubility Parameter which is known as anumerical estimate of intermolecular forces. It is generally known thatcompatibility is higher as a difference between SP values of twomaterials is smaller.

Therefore, the present inventors attempted to select a plasticizer usedin the present disclosure with an SP value as a clue. The SP value ofethylene acrylate rubber is estimated at 8 or more although it isdifficult to calculate an exact value because the SP value of the rubberdepends on the grade of the ethylene acrylate rubber. Therefore, samplesof ethylene acrylate rubber compositions are made with variousplasticizers having different SP values, and oil resistance, heatresistance and hydrolysis resistance of molded articles after moldingand cross-linking were evaluated. As a result, it has been found that aplasticizer with an SP value of 7 or more is effective. The SP value ofa plasticizer is more preferably 8 or more.

A plasticizer with an SP value of 7 or more is, preferably, at least oneplasticizer selected from the group consisting of a polyether esterbased plasticizer, a trimellitate ester based plasticizer, apyromellitate ester based plasticizer and a hydrogenated hydrocarbonbased plasticizer. Among such plasticizers, a trimellitate ester basedplasticizer is preferable because of kneading workability.

The polyether ester base plasticizer is given specifically ADKCIZER-RS735 (ADEKA CORPORATION) and ADK CIZER-RS700 (ADEKA CORPORATION)or the like.

The trimellitate ester based plasticizer is given specificallytri(2-ethylhexyl) trimellitate, tri-n-octyl trimellitate, triisodecyltrimellitate, triisononyl trimellitate and higher alcohol ester mixedwith trimellitate or the like are given specifically.

The pyromellitate ester based plasticizer is given specificallytetra(2-ethylhexyl) pyromellitate, tetra-n-octyl-pyromellitate or higheralcohol ester mixed with pyromellitate or the like are givenspecifically.

The hydrogenated hydrocarbon based plasticizer is given specificallyDurasyn series (INEOS Oligomers) or the like are given specifically.

An amount of 10 to 50 parts by mass of a plasticizer with an SP value of7 or more is mixed with 100 parts by mass of ethylene acrylate rubber.The amount of a plasticizer with an SP value of 7 or more is preferablyset to 10 to 30 parts by mass, more preferably 10 to 20 parts by mass.When a plasticizer with an SP value of 7 or more is mixed as describedabove, an ethylene acrylate rubber composition satisfies goodworkability, heat resistance, oil resistance and hydrolysis resistancewith good balance.

Although a plasticizer with an SP value of 7 or more and a plasticizerwith an SP value below 7 may be mixed and used, plasticizer bleed-out ofthe plasticizer with an SP value below 7 may occur and workability maydecrease. Therefore, an amount of the plasticizer with an SP value below7 is set to less than 0.7 parts by mass regarding to 10 to 50 parts bymass of a plasticizer with an SP value of 7 or more, when the bothplasticizers are mixed and used.

(Cross-Linking Agent)

As described above, an ethylene acrylate rubber cross-linked topolyvalent aliphatic primary amine or derivatives thereof is used as theethylene acrylate rubber. Therefore, a cross-linking agent employs oneselected from polyvalent aliphatic primary amine or derivatives thereof.

The polyvalent aliphatic primary amine which can be used as thecross-linking agent is aliphatic polyamine such as hexamethylenediamine, N,N-dicinnamylidene-1, 6-hexane diamine, diethylene triamine,triethylenetetramine, tetraethylene pentamine, pentaethylene hexamine,ethylene diamine, 1,4-diaminobutane or the like.

Moreover, hexamethylene diamine carbamate or the like are given to thepolyvalent aliphatic primary amine derivatives. Such polyvalentaliphatic primary amine or derivatives thereof may be used alone or witha combination of two or more.

The cross-linking agent of 0.05 to 30 parts by mass selected from thepolyvalent aliphatic primary amine or the derivatives thereof is addedto 100 parts by mass of an ethylene acrylate rubber. Preferably, theamount of the cross-linking agent is 0.1 to 10 parts by mass and morepreferably, 0.3 to 1 parts by mass.

(Cross-Linking Promoter)

Besides the cross-linking agent, a cross-linking promoter may be used incombination. The cross-linking promoter preferably employs a basiccross-linking promoter in combination. The basic cross-linking promoteremploys a guanidine compound, 1, 8-diazabicyclo [5.4.0] undec-7-ene(DBU), 1, 5-diazabicyclo [4.3.0] nonene-5 or the like. The cross-linkingpromoter as mentioned above is commercially available to Vulcofac ACT55(Safic-Alcan) or the like. Such cross-linking promoters are added to 100parts by mass of ethylene acrylate rubber at 0.05 to 20 parts by mass,preferably 0.1 to 10 parts by mass.

An ethylene acrylate rubber composition preferably contains at least oneof 20 to 150 parts by mass of carbon black or 20 to 150 parts by mass ofsilica relative to 100 parts by mass of the ethylene acrylate rubber.

(Carbon Black)

Carbon black is added in order to reinforce an ethylene acrylate rubbercomposition. Examples of the carbon black are given SRF, GPF, FEF, HAF,MAF, ISAF, SAF, FT, MT or the like but not specifically limited. The MAFand SRF may be suitably used. Moreover, such carbon black may be usedalone or with a combination of two or more. A commercially availableproduct is Seast, grade: G-S (TOKAI CARBON Company limited) or the like.

Carbon black is preferably mixed with an ethylene acrylate rubber at 20to 150 parts by mass relative to 100 parts by mass of ethylene acrylaterubber. When the amount of carbon black is less than 20 parts by mass,it may be difficult to maintain the tensile strength of the ethyleneacrylate rubber. Moreover, when the amount of carbon black is over 150parts by mass, a kneading process and a molding process may bedifficult. It is more preferable that the amount of carbon black is setto 30 to 100 parts by mass.

(Silica)

Silica is mixed in order to reinforce an ethylene acrylate rubbercomposition. The silica is given to a precipitated silica, a colloidalsilica, a gas phase process silica and an organo silica or the like asexamples. Among such silica, the precipitated silica is preferable. Acommercially available product of the precipitated silica is givenNipsil series (Tosoh Silica Corporation) or the like as examples. Acommercially available product of the colloidal silica is given SNOWTEXseries (Nissan Chemical Corporation) or the like as examples. Moreover,a commercially available product of the gas phase process silica isgiven AEROSIL series (NIPPON AEROSIL CO., LTD) or the like are given asexamples. As a commercially available organo silica, SNOWTEX series(Nissan chemical Corporation) or the like are given as examples.

Silica is preferably mixed with an ethylene acrylate rubber at 20 to 150parts by mass per 100 parts by mass of ethylene acrylate rubber. Whenthe amount of silica is less than 20 parts by mass, it may be difficultto maintain the tensile strength of the ethylene acrylate rubber.Moreover, when the amount of silica is over 150 parts by mass, akneading process and a molding process may be difficult. The amount ofsilica is more preferably set to 20 to 80 parts by mass.

Besides above components, where necessary, a known mixing agent such asa processing agent, a reinforcing agent, a filler, an anti-aging agent,a stabilizer or the like may be added to the ethylene acrylate rubbercomposition. For example, a processing aid such as stearic acid and anacid acceptor such as zinc oxide, magnesium oxide or the like is given.

(Cross-Linked Molded Article of an Ethylene Acrylate Rubber Composition)

In order to produce a cross-linked molded article formed of an ethyleneacrylate rubber composition, the ethylene acrylate rubber composition isobtained first by adding a predetermined cross-linking agent,cross-linking promoter or the like. Then, the ethylene acrylate rubbercomposition is molded and cross-linked. The order in which the moldingstep and the cross-linking step to produce the cross-linked moldedarticle is not specifically limited and the order may be determined byshapes of materials or the like. Therefore, the molding step may beperformed prior to the cross-linking step, or the cross-linking step maybe performed prior to the molding step, or the molding step and thecross-linking step may be performed simultaneously.

A kneading machine to prepare an uncross-linked ethylene acrylate rubbercomposition (i.e., a rubber compound) may be a known kneading machinesuch as a single-screw extruder, a twin-screw extruder, a roll, aBanbury mixer, a kneader, a high shear mixer or the like. A method andan order in which respective components composing the ethylene acrylaterubber composition are added to the mixer are not specifically limited.

A molding method to produce a molded article of the ethylene acrylaterubber composition is not specifically limited. The method may employany of a compression molding method, an injection molding method, anextrusion molding method and a transfer method.

The cross-linking process which cross-links the uncross-linked ethyleneacrylate rubber composition may be performed in a single stage, or intwo stages divided in a first cross-linking stage and a secondcross-linking stage. The second cross-linking stage after completion ofthe first cross-linking stage is performed to securely cross-link theethylene acrylate rubber composition up to the internal portion Ingeneral, cross-linking is performed under the pressurized cross-linkcondition at about 150° C. to 230° C. and for about 0.5 min to 30 min.The second cross-linking stage is generally performed by oven heating atabout 150° C. to 250° C. and for about 0.5 hrs to 24 hrs.

The molded article composed of the cross-linked ethylene acrylate rubbercomposition may be widely used in various situations such as a transportmachine like an automobile, general equipment, electronic electricalequipment, a building material and a hose. Especially the molded articleis useful as a sealing member such as a gasket, an O-ring, a packing, anoil sheet, a bearing seal or the like.

EXAMPLES

The present disclosure will be described in detail referring toExamples.

Examples 1˜4, Comparative Examples 1˜3

Raw materials of the ethylene acrylate rubber compositions used inExamples and Comparative Examples are the followings.

-   -   Ethylene acrylate rubber (AEM): Vamac (Registered Trademark)        Ultra HT-OR, high temperature/oil resistance grade (DuPont        Elastomers LLC.)    -   Acrylate rubber (ACM): NOXTILE PA522HF (UNIMATEC Co., LTD)    -   Plasticizer: Trimellitate ester base plasticizer, ADK CIZER        C-9N, SP value: 8.5 (ADECA)    -   Plasticizer: Polyether ester base plasticizer, ADK CIZER RS700,        SP value: 8.9 (ADECA)    -   Plasticizer: Hydrogenated hydrocarbon base plasticizer, Durasyn®        164, SP value: 7.9 (INEOS Oligomers)    -   Plasticizer: Paraffin base, Diana Process oil PW380, SP value:        6.6 (Idemitsu Kosan Co., Ltd)    -   Carbon black: SRF carbon black, Seast, grade: G-S (TOKAI CARBON        Company limited)    -   Silica: Nipsil E74P (Tosoh silica corporation)    -   Cross-linking agent: hexamethylene diamine carbamate    -   Cross-linking promoter: DBU (diazabicyclo undecene)

Rubber pastes of ethylene acrylate rubber compositions were prepared bymixing the components listed in Table 1 each other by using a sealedkneading machine and an open roll. The obtained rubber pastes werepressed to obtain uncross-linked rubber sheets with a thickness of about3 mm. Then, the uncross-linked rubber sheets were cross-linked in apress cross-link process and a second cross-link process to obtaincross-linked rubber sheets with a thickness of 2 mm. The presscross-link condition was at 180° C. for 6 minutes and the secondcross-link condition was at 175° C. for 15 hrs.

<Evaluation of Performance of Cross-Linked Rubber Sheet> (1) Workability

Workability was evaluated as to whether significant plasticizerbleed-out occurred on uncross-linked rubber sheets, press cross-linkedrubber sheets and secondary cross-linked rubber sheets, or not.

Criterion for workability: When a small amount of plasticizer bleed-outoccurred, the workability was evaluated as “good”. When a large amountof plasticizer bleed-out occurred, the workability was evaluated as “nogood”.

(2) Oil Resistance

The cross-linked rubber sheets were immersed in JIS No. 3 oil at 150° C.for 70 hrs and the differences in the hardness of the rubber sheetsbefore and after immersed in the hardness and the volume change ratewere measured. The tests were conformed to JIS K 6258 and Durometer (Atype) was used to measure the hardness.

Criterion for oil resistance: When the difference in the hardness was−20 or less, the oil resistance was evaluated as “good”. When the volumechange rate was +30 or less, the oil resistance was evaluated as “good”.

(3) Hydrolysis Resistance

The cross-linked rubber sheets were immersed in a solution under twodifferent conditions described below and the differences in the hardnessof the rubber sheets before and after the immersed and the volume changerates were measured. The tests were conformed to JIS K 6258 and thehardness was measured by Durometer (A type).

The immersion condition for hydrolysis resistance 1: Immersing in asolution containing 1% by mass of ZnCl₂ at 120° C. for 480 hrs andthereafter drying at 120° C. for 70 hrs.

The immersion condition for hydrolysis resistance 2: Immersing in asolution containing 1% by mass of ZnCl₂ at 150° C. for 200 hrs.

The criterion for hydrolysis resistance 1: When the difference in thehardness was +20 or less, the hydrolysis resistance was evaluated asgood. When the difference in the hardness was over +20, the hydrolysisresistance was evaluated as poor.

The criterion for hydrolysis resistance 2: When the difference in thehardness was +20 or less, the hydrolysis resistance was evaluated asgood. When the difference in volume change rate was +50% or less, thehydrolysis resistance was evaluated as good.

Evaluation results of the cross-linked rubber sheets are listed in Table1.

TABLE 1 Comparative Comparative Comparative Items Contents Unit Example1 Example 2 Example 3 Example 4 Example 1 Example 2 Example 3Composition AEM Polymer Vamac Ultra parts by 100 100 100 100 100 100 —HT-OR mass ACM Polymer Noxtite parts by — — — — — — 100 PA522HF massPlasticizer ADK CIZER parts by 10 20 10 10 — 10 — (Trimellitate C-9N,mass ester based) SP value: 8.5 Plasticier ADK CIZER parts by — — 5 — —— — (Polysther RS700, mass seter based) SP value: 8.9 PlasticizerDurasyn 164, parts by — — — 5 — — — (Hydrogenated SP value: 7.9 massester based) Plasticizer Diana Process parts by — — — — — 5 — (Paraffinoil PW 380, mass based) SP value 6.6 SRF carbon Seast G-S parts by 40 4040 40 40 40 40 black mass Silica Nipsil E74P parts by 30 30 30 30 30 3030 mass Cross-liking hexamethylene parts by 0.9 0.9 0.9 0.9 0.9 0.9 0.9agent diamine mass carbamate Cross-linking DBU parts by 2.2 2.2 2.2 2.22.2 2.2 2.2 promoter (diazabicyclo mass undecene) PerformanceWorkability small Good Good Good Good Good Poor Good bleeding ofplasticizer: O, large bleeding of Oil resistance JIS No. 3, 150° C. × 70hrs Hardness Durometer, pts −17 −12 −15 −17 −23 — −17 change 

 Hs A type Volume change % +26.5 +21.4 +25.6 +28.5 +41.4 — +25.8 rate 

 V Hydrolysis Immersion Good Good Good Good Good Good Poor resistance 11 wt % ZnCl₂ solution, 120° C. × 480 hrs, Dry 120° C. × 70 hrsHydrolysis 1 wt % resistance 2 ZnCl₂ solution, 150° C. × 200 hrsHardness Durometer, pts +5 +7 +7 +9 +3 +11 Impossible change 

 Hs A type to measure Volume change % +1.3 −4.7 −5.1 −5.5 +3.0 −6.4 >100rate 

 V

As shown in results of Table 1, the cross-linked rubber sheets inExamples 1 to 4 were used of Vamac Ultra HT-OR, an ethylene acrylaterubber with a high temperature and oil resistance grade, and thehydrolysis resistances of the rubber sheets were improved without asignificant loss of oil resistance by adding a plasticizer having an SPvalue of 7 or more and high compatibility.

Since the cross-linked rubber sheet in Comparative Example 1 did notcontain any plasticizer, the oil resistance of the rubber sheet wasinferior to that of the cross-linked rubber sheet of acrylic rubber inComparative Examples 3.

The cross-linked rubber sheet in Comparative Example 2 had a paraffinbased plasticizer having a low SP value and poor compatibility withethylene acrylate rubber. Therefore, significant plasticizer bleed-outof the uncross-linked rubber sheet and the cross-linked rubber sheet wasdetected and the workability was worse.

The cross-linked rubber sheet in Comparative Example 3 employs anacrylic rubber and the hydrolysis resistance of the rubber sheet wassignificantly inferior to that of the ethylene acrylate rubber sheets.

1. An ethylene acrylate rubber composition comprising: 100 parts by mass of an ethylene acrylate rubber, 10 to 50 parts by mass of a plasticizer with an SP value of 7 or more, 0.05 to 30 parts by mass of a cross-linking agent which is selected from polyvalent aliphatic amine or derivatives thereof; and less than 0.1 parts by mass of a plasticizer with an SP value of below
 7. 2. The ethylene acrylate rubber composition according to claim 1 comprising at least one of 20 to 150 parts by mass of carbon black or 20 to 150 parts by mass of silica.
 3. The ethylene acrylate rubber composition according to claim 1, wherein the plasticizer with an SP value of 7 or more is one or more selected from the group consisting of a polyether ester based plasticizer, a trimellitate ester based plasticizer, a pyromellitate ester based plasticizer, and a hydrogenated hydrocarbon based plasticizer.
 4. A molded article formed of a cross-linked product of the ethylene acrylate rubber composition of claim
 1. 5. The molded article according to claim 4 is a sealing member.
 6. The ethylene acrylate rubber composition according to claim 2, wherein the plasticizer with an SP value of 7 or more is one or more selected from the group consisting of a polyether ester based plasticizer, a trimellitate ester based plasticizer, a pyromellitate ester based plasticizer, and a hydrogenated hydrocarbon based plasticizer.
 7. A molded article formed of a cross-linked product of the ethylene acrylate rubber composition of claim
 2. 8. A molded article formed of a cross-linked product of the ethylene acrylate rubber composition of claim
 3. 9. A molded article formed of a cross-linked product of the ethylene acrylate rubber composition of claim
 6. 10. The molded article according to claim 7 is a sealing member.
 11. The molded article according to claim 8 is a sealing member.
 12. The molded article according to claim 9 is a sealing member. 